This invention generally relates to weight classification systems for vehicles. More particularly, this invention relates to a calibration method for calibrating sensors used in a vehicle seat weight classification system.
Vehicle safety restraint systems have changed over the years. Seat belts have proven effective at minimizing injuries during accidents. Additional safety devices have been introduced such as air bags. While air bags provide additional benefits, it has become apparent that individualized air bag control would be beneficial. More recently, systems for classifying the weight of a seat occupant have been developed that allow for individualized control of an air bag.
One example weight classification system includes a plurality of sensors within a seat base portion of the seat. The sensors provide electrical signals indicative of the seat occupant""s weight. These signals are processed and utilized to determine an air bag deployment strategy according to selected guidelines.
One issue presented by such weight classification systems is the possibility for the sensors to become less accurate over time. One issue that must be accommodated is the possibility for material offset drift, which may have an effect on the accuracy of the weight determination. Because the characteristics of a vehicle seat change over time, the performance of the sensors associated with that seat may also change. Therefore, there is a need to recalibrate or accommodate changes in the system over time.
This invention addresses the need for automatically recalibrating a weight classification system to compensate for changes in system performance such as material offset drift.
In general terms, this invention is a system and method for recalibrating a vehicle seat weight classification system. A system designed according to this invention includes a plurality of sensors in the vehicle seat that provide signals indicating the weight of a load on the seat. A controller communicates with the sensors. The controller also determines when a calibration condition exists. The controller samples outputs of each of the sensors, preferably when there is no load on the seat. The sample sensor outputs preferably are taken intermittently over a selected period of time. The controller determines an average value of the sensors outputs. The average value is then compared to a current calibration value and, if selected conditions are met, the new average value is substituted for the calibrated value. Accordingly, each sensor of the weight classification system can be individually recalibrated to compensate for changes in the system over time.
A method of this invention includes several basic steps. The method preferably begins by determining when a calibration condition exists. If the calibration condition exists, a plurality of outputs of the system sensors are sampled over a selected period. An average output of each sensor is determined using the sampled outputs. If the average is within a selected range then the corresponding sensor is recalibrated using the average value.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows.